1. Field of the Invention
The present invention relates to the field of display, and in particular to the field of mura phenomenon compensation method for display panel and display panel.
2. The Related Arts
Because of various defects in the manufacturing process of liquid crystal display (LCD), the manufactured LCD panel may have non-uniform luminance and display various mura phenomena (the mura phenomenon refers to the marks caused by non-uniform luminance of the display panel.)
To improve the luminance uniformity of the display panel, some mura compensation methods are developed. For example, an external high-resolution camera is used to take a few grayscale frames (pure white screen with different luminance) mura forms. By comparing the brightness of the center position of the display panel, the brightness difference between the surrounding area and the center position is computed, and then compensates the grayscale value of the mura location (by reducing the grayscale value for area brighter than the center position to reduce brightness, and increasing the grayscale value for area darker than the center to increase brightness) to make the display panel as a whole to achieve a more consistent brightness.
In general, the reverse compensation data is stored in flash memory. Also, to reduce cost, the flash memory does not store the grayscale compensation data for each pixel. The known approach is to compress an area of n*n pixels (for example, 8*8 pixels), and each area stores the grayscale compensation data for one of the pixels in the flash. The other pixels in the area use grayscale compensation data calculated by linear interpolation.
Take Ultra High Definition (UHD) display panel (3840*2160 pixels—a display panel with 3840 columns and 2160 rows of pixels) as an example. Refer to FIG. 1, by compressing an 8*8 pixel area, the compression results in 480*270 areas (the dash square in the figure indicates an area). The data memory stores the mura compensation data corresponding to pixels at the intersections of the 1st, 9th, 17th, . . . , 2145th, 2153rd columns and the 1st, 9th, 17th, . . . , 3825th, 3833rd rows (indicated by the circled pixels). The total of 480*270 mura compensation data is stored. Moreover, to calculate the mura compensation data corresponding to the pixels of the 3834th-3840th columns and pixels of the 2154th-2160th rows, the stored mura compensation data corresponding to the 3825th column and 3833rd column are used to calculate to obtain the mura compensation data corresponding to the pixel of the 3841st column (virtual pixel with circle in the figure) with 270 mura compensation data. By using stored mura compensation data corresponding to the 2145th row and 2153rd row, the mura compensation data corresponding to the pixel of the 2161st row (virtual pixel with circle in the figure) is calculated to obtain 480 mura compensation data. Accordingly, the data memory needs to store 481*271 mura compensation data, and the mura compensation data for the remaining pixels are calculated by a timing controller (Tcon IC) based on linear interpolation with the existing 481*271 mura compensation data.
For the specific calculation for the remaining pixels, also refer to FIG. 1. Take area formed by the pixels of the 1st-8th row 1st-8th column (8*8 pixels) as example. In the area, assume that the pixel at the intersection of the 1st column and 1st row (left upper corner pixel) corresponds to a mura compensation value A′, the pixel at the intersection of the 9th column and 1st row corresponds to a mura compensation value B′, the pixel at the intersection of the 1st column and 9th row corresponds to a mura compensation value C′, the pixel at the intersection of the 9th column and 9th row corresponds to a mura compensation value D′, the pixel e′ corresponds to a mura compensation value E′, the pixel f′ corresponds to a mura compensation value F′, the pixel g′ corresponds to a mura compensation value G′; wherein, the mura compensation value A′, B′, C′, D′ are known values. After linear interpolation, the E′, F′ and G′ are calculated as follows:E′=[(8−Y′)*A′+Y′*C′]/8;F′=[(8−Y′)*B′+Y′*D′]/8;G′=[(8−X′)*E′+X′*F′]/8.
Wherein the X′ and Y′ are the number of pixels spaced apart between the corresponding pixel and the pixel at the intersection of 1st column and 1st row in the direction of row and column respectively.
However, when the mura change in an area is drastic, and the grayscale compensation data calculated by the above linear interpolation is used for compensation, as shown in FIG. 2, the area with drastic change in mura condition still shows apparent mura phenomenon (see FIG. 2 for the left and right ends of the display effect when uncompensated). The non-uniform luminance can still show after compensation; therefore, the known linear interpolation method is no longer sufficient to address the mura issue.